It is already known to provide remotely controlled switching devices for appliances such as television receivers. Typically, a television receiver, as purchased, includes a channel selector knob which fits on and is adapted to rotate a shaft projecting outwardly from the chassis of the television receiver. The shaft is typically of non-circular end section, and in most cases is semi-circular or nearly so. The control knob has a complementary recess for receiving this shaft.
One approach to making the television receiver remotely controllable is exemplified in U.S. Pat. No. 3,984,779. This patent, issued Oct. 5, 1976 to Hughes, discloses the provision of a motorized drive which includes a gear reducer and which provides low-speed high-torque rotary movement on a drive shaft having a semi-circular end section. Mounting means are provided to align this drive shaft with the control shaft projecting from and forming part of the television receiver. A cylindrical coupling is provided having two semi-circular openings at opposite ends, the one opening receiving the the drive shaft and the other fitting over the control shaft of the television receiver.
There is, however, a difficulty which arises in connection with the mounting of such a control assembly on an existing television receiver. The difficulty relates to the facts that (a) the control shaft for the television receiver has normally a specific number of discrete angularly separated positions in which it is "at rest" (on many television sets the control shaft cannot be turned to and left at an intermediate position between these discrete angular positions which correspond with the particular channels); (b) the drive shaft, which is rotatable through the gear reduction mechanism by (typically) a small electrical motor, cannot be turned by hand, due to the gear reducing mechanism. Now, in the case of the apparatus shown in U.S. Pat. No. 3,984,779, the housing for the motor, from which the drive shaft extends, has one particular orientation with respect to the housing for the television receiver, due to the way in which it is mounted. Hence, it is not possible to swivel the motor housing about with respect to the drive shaft in order to achieve a proper fit. Thus, if it happens that the "at rest" position of the control shaft extending from the television receiver is not exactly aligned rotationally with the drive shaft extending from the motor housing when it is in its mounted position, it will literally not be possible to position the coupling member between them. The drive shaft cannot be rotated, and typically the control shaft will not maintain itself in any intermediate position.
This latter problem is bound to create difficulties for the purchaser who has bought one of the control assemblies and who is attempting to mount it on his television receiver.
Accordingly, it is an aim of this invention to overcome the problem of angular mismatch between the output drive shaft of the drive means and the control shaft of the television receiver, or other appliance to which the assembly of this invention is to be fitted.